Connected and communicating vehicles are now the norm. Navigation systems regularly update their maps and show directions using satellite data and drivers make phone calls while driving. In the future, data exchange will play an even greater role in road transport, not least to improve road safety.

However, new options need to be found for housing antennas in cars. At TU Wien, researchers developed a special antenna box that can be integrated into the front area of the car roof.

This position is preferable for several reasons. It is available on most car types like sedans, hatchback, station wagons etc. and it can be combined with model variations such as sunroofs and panorama roofs. A front position is also closer to the control electronics (shorter cables). Intuitively antenna cavities could be tilted to follow the roof curvature … Instead, it is proposed to insert a horizontal cavity above the windshield, remove the front cavity wall and adjust the side walls to the roof curvature.

The position of an antenna on a car has a strong influence on the directions that it can cover and communication in driving direction is paramount for cooperative driving.

—Artner et al.

Detailed measurements show that the directionality of wireless signals is very good around cars, and with the new antenna variants cars are extremely well equipped for the wireless requirements of tomorrow.

Antennas in cars are usually installed in what is known as the shark fin. This is a compact attachment that is mounted on the rear of the car’s roof.

—Gerald Artner (Telecommunications, TU Wien)

However, it is not possible to house any number of antennas in this kind of shark fin attachment; first of all, there is not enough space, and second of all the antennas can interfere with one another when they are packed too tightly. This is problematic because the telecommunications capabilities of cars are expected to be significantly expanded in the coming years.

Communication between cars and fixed infrastructure is also expected, and even the ways in which communication between smartphones and vehicles could be utilized to improve road safety is being considered. With a mobile phone signal, the car could detect a pedestrian before they are even within view.

At TU Wien, the decision was therefore made to develop a new method for installing antennas in cars which overcame the upcoming technical challenges. Gerald Artner constructed an antenna box from carbon-fiber-reinforced polymer material which could be installed in the front part of the roof, close to the windshield.

In cooperation with the Thüringer Innovationszentrum Mobilität [Thuringian Centre of Innovation in Mobility] at TU Ilmenau in Thuringia, this kind of antenna cavity was built into a car roof for the first time. The entire car was then surveyed in the only research laboratory of its kind in Europe, the Virtual Road Simulation and Test Area (VISTA), in order to identify the resulting radiation patterns.

We have carefully analysed the directions in which the antennas in our antenna cavity transmit, and the intensity thereof. As demonstrated, our antenna cavity not only provides more space for a larger number of antennas, but the directionality is also better than a ‘shark fin’ at the rear. The antennas in the ‘shark fin’ often do not provide high transmission power directly forwards because they are shielded by the curvature of the car roof. Our antenna box gives excellent results right in this direction.

—Gerald Artner

It would also be possible to combine several antenna concepts in future cars. This would help compensate for any interference even more effectively.